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45 lines
1.6 KiB
Python
Executable File
45 lines
1.6 KiB
Python
Executable File
##
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## This file is part of the libsigrokdecode project.
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##
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## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de>
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##
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## This program is free software; you can redistribute it and/or modify
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## it under the terms of the GNU General Public License as published by
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## the Free Software Foundation; either version 2 of the License, or
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## (at your option) any later version.
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##
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## This program is distributed in the hope that it will be useful,
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## but WITHOUT ANY WARRANTY; without even the implied warranty of
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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## GNU General Public License for more details.
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##
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## You should have received a copy of the GNU General Public License
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## along with this program; if not, write to the Free Software
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## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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##
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'''
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This decoder stacks on top of the 'usb_signalling' PD and decodes the USB
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(low-speed and full-speed) packet protocol.
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Protocol layer (USB spec, chapter 8):
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Bit/byte ordering: Bits are sent onto the bus LSB-first. Multibyte fields
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are transmitted in little-endian order (i.e., LSB to MSB).
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SYNC field: All packets begin with a SYNC field (8 bits).
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Packet field format: Packets start with an SOP (Start Of Packet) delimiter
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that is part of the SYNC field, and end with an EOP (End Of Packet).
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PID: A PID (packet identifier) follows the SYNC field of every packet. A PID
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consists of a 4-bit packet type field, and a 4 bit check field.
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The check field is the one's complement of the packet type field.
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Details:
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https://en.wikipedia.org/wiki/USB
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http://www.usb.org/developers/docs/
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'''
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from .pd import Decoder
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